How do i know if my leopard gecko is lacking calcium?

I have 2 Female leopard geckos and recently over the past week or so they're tails have become alot thinner than usual. We feed them on crickes every 2-3days but over the last month and a half have not been dusting them due to having a large container of them and it is difficult to stop them all getting out however we do have a bowl of calcium in the tank. Also we have been taking them out and letting them wander around the room alot so is it possible that this could be the result of them getting thinner as they are using more energy?